Sheet metal resistance welding pin

ABSTRACT

A resistance welding pin formed of sheet metal adapted to attach insulation to a duct or the like. The pin includes a head portion and a shank portion and is characterized by the shank portion being folded, and including elements both substantially in the plane of and normal to the plane of the head. The portions of the shank disposed in the plane are recessed or cut away to define a weakened area to facilitate a controlled relative flexing movement between the shank and the head. The pin includes a contact portion adapted to engage an electrode, the recessed or weakened portion being out of the circuit between the contact portion and the tip portion which is actually affixed to the duct.

United States Patent Hinden et al.

[54] SHEET METAL RESISTANCE WELDING PIN [72] Inventors: Milton Hlnden,Massapequa, N.Y.;

David Porat, Brookline, Mass.

[73] Assignee: Duro-Dyne Corporation, Farmingdale, N.Y.

[22] Filed: Aprll30,1971

[21] Appl. No.: 138,901

[52] US. Cl. ..219l98, 85/11 [51] Int. Cl. ..B23k 9/00 [58] Field oiSearch ..2l9/98, 99; 85/11, 16; 287/202 WS [56] References Cited UNITEDSTATES PATENTS 1,605,695 11/1926 Baloyan..'. .Q ..85/16 2,740,505 4/1956Flora ..85/l1 X 2,751,052 6/1956 Flora, .(85/11 X Y 51 Oct. 3'l, 1972Primary Examiner-C. L. Albrit'ton Attorney-Mark T. Basseches and PaulaT. Basseches [5 7] ABSTRACT A resistance welding pin formed of sheetmetal adapted to attach insulation to a duct or the like. The pinincludes a head portion and a shank portion and is characterized by theshank portion being folded, and including elements both substantially inthe plane of and normal to the plane of the head. The portions of theshank disposed in the plane are recessed or cut away to define aweakened area to facilitate a controlled relative flexing movementbetween the shank and the head.

The pin includes a contact portion adapted to engage an electrode, therecessed or weakened portion being out of the circuit between thecontact portion and the tipportion which is actually affixed to theduct.

10 Ilaims, 4 Drawing Figures l-logg "219/99 faces:

. l 1 SHEET METAL RFSIS .CE PIN BACKGROUND OFTHEINVENHON 1.Field'ofthelnvention This'invention'is in the field of resistancewelding pinsv adapted tosecure insulative material to duct sur- Inrecent years in heating and cooling conveying purposes of reducing heatexchange between the conveyed fluid and the surrounding area have becomein- FOR ATTACHINGINSULATION TO DUCT WORK;

Ser. No. 49,253, now .us. Pat. No. 3,591,763 enti led METHOD ANDAPPLICATOR' PIN FOR AT- q systems, the use of steelor like ducts havinginsulative material internally or externally supported thereon forTACHING INSULATOR MATERIAL TO DUCT S RESISTANCE WELDING; and Ser. No.49,254,'now US. Pat. No. 3,591,762 entitled WELDING AP- PARATUS; I

2. The Prior Art l-leretofore resistance welding pins for attachingindefine an essentially circular puddleor weld area of attachment to theduct. The connection between such welding pins and the duct material hasbeen found to be durable and reasonably resistant to forces acting tofracture or dislodge the weld connection. I

.lt'will be appreciated that in some instances the sheet metal with theinsulative material already attached may be stacked, shipped and/orsubjected to forming steps,

such as bending, etc. Accordingly, the ability of the welding pin toresist separation from the duct is an important attribute of an attachedwelding pin.

Certain drawbacks inhere in connection with welding pins of the typedescribed, i.e., of cylindrical shanks and large circular heads. Amongsuch drawbacks may be mentioned high expense of fabricating thecylindrical type pins, and the large cubic area occupied by each suchpin, with resultant bulkiness of packages containing a large quantity ofpins.

Experiments intended to enable the production of a satisfactory weldingpin fabricated of sheet metal have been undertaken, but such experimentshave been unsuccessful prior to the present invention.

Initial experimental sheet metal resistance welding pins have been foundto provide only a weak weld connection. In instances where the weldconnection was found satisfactorily to resist tensile forces exertedagainst the pin and tending to draw the pin away from the duct, the weldhas been deficient in resisting lateral tilting forces exerted againstthe head, with a resultant separation of the weld.

In many instances, in order to achieve a satisfactory conductivityrelation'between the tip of the weld pin and the duct, considerableforces must be exerted against the of the weld pin in the direction ofthe duct. Such forces are required by the occasional presence of scaleor bits of insulation, adhesive, etc.

between the tip of the pin and the duct. Many of the sheet metalresistance welding pins tested have become bent or distorted before thepressures necessary to secure a proper weld have been developed.

1 Toovercorne these objections, experimental sheet metal pins ofprogressively heavier gauge were fabricated and tested. While suchheavier gauge .pins

.. facilitate the development .of satisfactory welding pressures, thepins, once attached, did not provide a connection satisfactorily able toresist fracturing of the weld, especially responsive to tilting forcesexerted as i tthe h a i I The heavier gauge pins had, in addition, theobviously undesirable characteristics of increased cost, and requi edthe use of heavier, and hence intricate and expensive, blanking and dieforming equipment.

suwMARY OF THE INVENTION The present invention maybe summarized asrelating to .a resistance welding pin. fabricated of sheet metalcomprising a head and shank, the shank terminating in a sharpened tip.The shank is bent at right angles; along the length thereof and includesportionsdisposed in the plane of the head. The junction of the shank andhead is defined by a weakened area, providing a degree of flexibilitybetween the shank and the head so that substantial components ofstresses applied to the head are not transmitted to the shank but,rather, application of such stresses inducesa yieldability and flexuralmovement between the head and the shank. I

The shank includes a contact portion, which portion is disposed betweenthe tip of the shank and the junction of the shank and head, the contactportion forming the position for the application of the primarycompressive 'forces exerted against the pin to achieve a weld. By

v this 'means, the low resistance area defined by the weakenedconnection between the shank and the head is not in the current flowpath utilized in the attachment of the welding pin. 1

Optionally but preferably, the contact portion is disposed to the sideof the plane of the head opposite from the tip of the shank. The shankportion between the contact portion and the tip is preferably bent or Tfolded about a bend or fold axis extending longitudinally of the notedportion of the shank to define an essentially three dimensional shankportion.

In a preferred embodiment, the welding pin is formed from an essentiallysquare metal blank, the

shank defining portion being separated from the remainder of the "blankby a pair of slits extending parallel to and to opposite sides of adiagonal of such square. The slits preferably extend beyond theintersection with the other diagonal of the square, i.e., are cut acrossmore thanhalf of the diagonal length of the blank.

Preferably the terminal ends of the slits defining the junction of theshank and the head include enlargements or recess cutouts extending intothe shank to define a bend or flexure area extending transversely of theshank. Flexure in this area may be facilitated by the provision ofmultiple score lines or recesses extending transversely of the shank inthis area. Preferably additional score lines extending normal to thefirst mentioned score lines may be provided to enable the head to tiltin a direction perpendicular to the tilt direction permitted by thefirst mentioned transverse score lines.

The thus formed shank is preferably bent at right angles transversely sothat the tip which is defined by a corner of the original blank isdisplaced to one side of the plane of the head.

The tip is sharpened either by a grinding or swaging operation, toprovide a point of the smallest possible area.

Preferably the transverse bend in the shank is disposed to the side ofthe plane of the head opposite from the tip so that welding pressuresurging the tip against a duct will be mainly or exclusively transmittedthrough the shank. I

Preferably the portion of the shank between the bend and the tip is bentabout a bend or folding axis which extends longitudinally of suchportion to a three dimensional configuration.

It is accordingly an object of the invention to provide a resistancewelding pin which is comprised of sheet metal.

A further object of the invention is to provide a pin of the typedescribed wherein the requisite pressures for achieving a satisfactoryweld may be readily developed without danger of distorting the pin.

Still a further object of the invention is the provision of a resistancewelding pin of the'type described which will, after connection to a ductor the like, be effective to hold the insulation in a selected positionand to protect the weld from the tendency to fracture or becomedislodged responsive to' stresses in any direction applied against thehead of the pin.

It is a still further object of the invention to provide a sheet metalresistance welding pin which may be inexpensively manufactured and whichis susceptible to being nested or stackedso as to enable packaging of amultiplicity of pins in a relatively small container.

To attain these objects and such further objectsas may appear herein orbe hereinafter pointed out, reference is made to the accompanyingdrawings, forming a part hereof, in which:

FIG. 1 is a plan view of a metal blank from which the pin is formed;

FIG. 2 is a plan view of .the blank in position for engagement;

FIG. 3 is a cross section taken on the line 3-3 of FIG. 2;

FIG. 4 is a cross section taken on the line 4-4 of FIG. 2.

Referring now to the drawings, the resistance welding pin in accordancewith the invention comprises a metal blank member which is essentiallysquare in plan. The blank, which is preferably formed in a stampingoperation, may be of approximately 18 gauge metal where the same is tobe used with welding apparatus having about 60 amperes welding current.

The welding pin may include a head portion 11 and a shank 12. Thelongitudinal axis 13 of the shank 12 preferably coincides with one ofthe diagonals of the square blank l0.

4 The shank 12 terminates in a sharpened tip 14, the

sharpness of the tip resulting both from the fact that the tip coincideswith the corner configuration of the shank plus the angularly directedbevels 15, 16. It will be appreciated that the bevels maybe formed onone or both sides to provide a tip 14 which is as sharp as. possible,defining a cross sectional area which is only a small fraction of thearea of the major length of the shank.

The shank 12, which is formed in the course of the stamping operation,is defined by a pair of elongated cutouts 17, 18, which cutoutsgenerally parallel the diagonal 13 and are spaced to opposite sidesthereof.

It will be observed that the junction portion or neck 19 of the shank,where the shank merges into the head 11, is narrowed as respects themajor length of the shank. The narrow neck 19 is defined by enlargedcutout portions 20, 21 formed at the end of the slits 17, 18,respectively. Preferably in the same operation, or in a separateoperation, the neck portion 19 is scored, as at 22, with transverselyextending score lines, such lines having the effect of reducing theforcesrequired to bend or flex the head of the welding pin relative tothe shank about a bending axis which parallels the neck area.

Optionally, an additional set of diagonally directed score lines 23extend outwardly from the neck area 19 to the corner 24 opposite the tip14, it being understood that the score lines 23permit relative pivotalmovement between the head and the shank about an axis perpendicular tothe 'pivot axis provided by the score lines 22.

As best understood by an inspection of FIGS. 1, 2 and 4, the shankportion 12 is preferably bent to an arcuate conformation or to a likethree dimensional attitude so as to increase the rigidity thereof.

It will be understood that the bending or folding step is preferablycarried out about a bending or folding axis parallel with the diagonal13. The bending step may be carried out in the same apparatus employedto blank or stamp the member 10, or in a separate operation.

The thus formed blank is thereafter bent to define a completed weld pinby a single or multiple fold step which forms the pin to theconfiguration seen in FIG. 4. Preferably the shank is not defined by asingle right angle bend but, rather, is formed by multiple folds whichdefine a raised contact area 25 -see FIGS. 2 and 4, which area ispreferably disposed in a plane above or to the side of the plane definedby the head 11 opposite from the side occupied by the tip 14. As bestseen in FIG. 2, it is important to note that the contact area 25 isdisposed between the reduced neck 19 and the tip 14. i

The method of applying the welding pin does not vary significantly fromthat described in my aforementioned United States patent applications.Specifically, the insulation material 26 whichhas previously beendisposed against the surface 27 of the duct 28 is locked to the surfaceby pressing the tip 14 downwardly into contact with the duct 28 throughthe application of a force against the contact portion 25 by anelectrode member 29. It will be appreciated that since the contactportion is preferably disposed in a plane above the head, downwardpressure exerted by the electrode is not transmitted to the head properbut, rather, to the contact portion. By reason of the arcuateconfiguration of the shank 12 substantial downward pressure by theelectrode may be effected without bending or deflection of the shank. 7

When a sufficient pressure is achieved, a welding current is passedthrough the shank, the circuit path of such current being from thecontact portion, through the length of the shank, and into the duct 28,the duct of course having previously been connected to the otherelectrode in the welding system. Thepassage of weldingcurrent willeffect a melting of the portion of the shank of smallest cross section,i.e., the tip, the moulten material fusing with the metal of the duct toeffect a firm attachment. The attachment of the pin to the duct providesa reasonably high tensile strength connection between the aforementionedparts.

By reason of the relatively wide bat thin co guration of the shankportion, it will be observed that the V weld which is formed provides aconnection which is resistant to fracture responsive to the applicationof rocking forces in the direction of the arcuate arrow 30, FIG. 3. Inother words, since an elongated weld formation is defined, rocking inthe direction of the arrow 30 is unlikely to fracture the connectionbetween the pin andthe duct; H

It will be appreciated that such rocking forces wonld be appliedresponsive to a downward pressure exerted against portions 31 or 32 ofthe head of the weld pin. When viewed in the direction of FIG. 4,however, it will i be appreciated that a fracture of the weld would befar more likely if a rocking force in the direction of the area 33 wereapplied to the shank. This greater tendency to fracture is occasioned bythe short lever arm due to the narrow extent of the weld.

In other words, referring back to FIG. 3, it willbe appreciated that,due to the length of the weld, the forces which tend to lift andfracture the weld may be satisfactorily combatted, whereas the sameisjnot true in the orientation shown in FIG. 4. It is the tendency ofweld pins to become separated when subjected to stresses shown in thedirection of the arrow 33 that has heretofore precluded the use of sheetmetal welding pins wherein the transverse extend'of the shank greatlyexceeds the thickness thereof.

I have discovered that by the provision of the weakened neck area 19alone or when coupled with'the transverse scoring 22, forces which wouldtend to stress the shank in a weld breaking direction represented by thearrow 33, FIG. 4, are absorbed in large measure by a flexure of the headrelative to the shank. Thus, a downward pressure at the points 34, 5will not result in the application of substantial tilting forces to theshank 12. Instead, the head will tend to tilt about the axis of the line22 extending transversely of the neck, with the transmission of onlyminimal tilting forces to the shank proper. 4

A phase of the inventive concept hereof may thus be said to lie in theunobvious and unexpected provision of a welding pin which is renderedless likely to separation from a duct by weakening or reducing thestrength of portions of the pin proper, so as to channel the forcesapplied against the pin in directions least likely to induce a fractureof the weld.

To a lesser degree, the score lines 23 permit some measure of flexure ofthe weld relative to the shank. However, as noted above, the pin is notlikely to be 6 dislodged responsive to tilting forces applied in theplane of the major faces of the shank.

It is important to note that the contact area 25 is formed between thenarrowed neck area'and the tip of the By p s ng h tac p ion a thi p stion, and by locating the contact portion above the level of the planeof the head, the narrowed n ck por tion will not lie within the path ofthe welding current. Thus, there is no substantial tendency forlocalized overheating in the neck area, as would otherwise be the caseif the neck were in the current flow path or if the contact portion atthe time of welding were not above or at least in the plane of the head.

Preferably the contact portion 25 provides a flat area parallel with thehead so that the downward forces against the pin which are exerted bythe welding electrode 29 are transmitted through alarge contact areaparallel with the under surface of the electrode and the upp Surface O educ From'the foregoing it will be appreciated that there is I provided asheet metal resistance welding pin particularly adapted for securinginsulation to the surface of a duct, the weld connection between the pinand the duct being resistant .to dislodgment' or fracture responsive tothe forces most often encountered by the pin.

It will be further understood that welding pins of the present inventionmay be compactly packaged in partially nesting condition, as shown inFIG. 2 for instance, wherein a second welding pin 10a has its headdisposed atop the pin 10, with the shank of the pin 10a disposed theopening defined by the downwardly bent shank 12 of the pin 10.

By providinga contact portion for the'electrode so located that thecurrent path does not traverse the weakened neck portion, the danger oflocalized over heating in the course of forming the weld is eliminated.

It be readily appreciated that a wide. amut of variations in the form ofwelding pins may be made without departing from the spirit of theconcepts hereinabove disclosed. By way of example, the shape of thehead, the shape of the shank, the shape and position of the weakenedflexure points in the shank, etc., may be varied within areasonably widerange, with the thus formed pins nonetheless incorporating the advancesof the present invention. Accordingly, the invention is to be broadlyconstrued within the scope of the appended claims.

Having thus described the invention and illustrated its use, what isclaimed as new and is desired to be secured by Letters Patent is:

l. A resistance welding pin integrally formed of sheet metal forattaching insulation to a duct or the like comprising a head and ashank, said shank being elongated and bent at right angles to said head,and including a sharpened tip at its free end disposed to one side ofthe plane of said head, a contact portion formed on said shank to theopposite side of said plane in the area between said bend and thejunction of said shank and head, and recess portions defining a weakenedarea of said shank, said recess portions being disposed between saidjunction and said contact portion of said shank.

:2. The pin of claim 1 and including weakened score lines extendingtransversely of said shank in the area between said junction and saidcontact portion.

3. A resistance welding pin for attaching insulation to a duct or thelike, said pin being integrally formed of an essentially square sheetmetal blank, said pin including a head portion and a shank, said shankbeing defined by a spaced pair of slits paralleling and spaced toopposite sides of a diagonal of said square, the comer of said squareincluded between said slits defining the tip of said pin, said shankbeing bent substantially at right angles in the area between said tipand the junction of said shank and said head.

4. A resistance welding pin in accordance with claim 3 wherein said tipis bevelled in an angular direction with respect to the plane of saidshank to define a sharpened point.

5. A resistance welding pin in accordance with claim 3 wherein saidshank is recessed in the area between said bend and said junction todefine a weakened portion of said shank.

6. A resistance welding pin in accordance with claim 5 and includingscore lines extending transversely of said weakened portion of saidshank.

7. A resistance welding pin of claim 6 and including score lines in saidhead extending substantially normal to said transverse score linestoward said corner of said blank opposite said tip.

8. A resistance welding pin in accordance with claim 3 wherein saidshank portion between said bend and said tip is bent to a threedimensional configuration about a bend axis parallel with the length ofsaid shank portion.

9. A resistance welding pin in accordance with claim 3 wherein saidright angular bent portion of said shank is disposed to one side of theplane of said head and said tip is disposed to the other side of saidplane.

10. As a new article of manufacture, a nested stack of resistancewelding pins for attaching insulation to a duct or the like, the pins ofsaid stack each defining an integral sheet metal element comprising ahead portion and a shank portion bent at right angles to said headportion and terminating in a sharpened tip, the shank portion of eachpin being formed by a pair of slits extending inwardly from theperimeter of said head portion, the distance between all opposedportions of the walls defining said slits being greater than thetransverse dirnension of said shank at the portion of said shankimmediately below said head, said welding pins being stacked with theunder surface of the head portion of each pin disposed parallel to andadjacent the upper surface of the head portion of the next lower pin andthe shank portion of each upper pin extending downwardly through thespace defined between the slits of the next lower pin and lying inparallel adjacent relation to the shank of said lower pin, whereby eachpin may be moved laterally relative to the next adjacent pin in aseparating direction of said shanks without interference between saidpins, the longitudinal axis of the shank of any pin in said stack beingangularly related to a line extending through the tips of said stack edpins.

1. A resistance welding pin integrally formed of sheet metal forattaching insulation to a duct or the like comprising a head and ashank, said shank being elongated and bent at right angles to said head,and including a sharpened tip at its free end disposed to one side ofthe plane of said head, a contact portion formed on said shank to theopposite side of said plane in the area between said bend and thejunction of said shank and head, and recess portions defining a weakenedarea of said shank, said recess portions being disposed between saidjunction and said contact portion of said shank.
 2. The pin of claim 1and including weakened score lines extending transversely of said shankin the area between said junction and said contact portion.
 3. Aresistance welding pin for attaching insulation to a duct or the like,said pin being integrally formed of an essentially square sheet metalblank, said pin including a head portion and a shank, said shank beingdefined by a spaced pair of slits paralleling and spaced to oppositesides of a diagonal of said square, the corner of said square includedbetween said slits defining the tip of said pin, said shank being bentsubstantially at right angles in the area between said tip and thejunction of said shank and said head.
 4. A resistance welding pin inaccordance with claim 3 wherein said tip is bevelled in an angulardirection with respect to the plane of said shank to define a sharpenedpoint.
 5. A resistance welding pin in accordance with claim 3 whereinsaid shank is recessed in the area between said bend and said junctionto define a weakened portion of said shank.
 6. A resistance welding pinin accordance with claim 5 and including score lines extendingtransversely of said weakened portion of said shank.
 7. A resistancewelding pin of claim 6 and including score lines in said head extendingsubstantially normal to said transverse score lines toward said cornerof said blank opposite said tip.
 8. A resistance welding pin inaccordance with claim 3 wherein said shank portion between said bend andsaid tip is bent to a three dimensional configuration about a bend axisparallel with the length of said shank portion.
 9. A resistance weldingpin in accordance with claim 3 wherein said right angular bent portionof said shank is disposed to one side of the plane of said head and saidtip is disposed to the other side of said plane.
 10. As a new article ofmanufacture, a nested stack of resistance welding pins for attachinginsulation to a duct or the like, the pins of said stack each definingan integral sheet metal element comprising a head portion and a shankportion bent at right angles to said head portion and terminating in asharpened tip, the shank portion of each pin being formed by a pair ofslits extending inwardly from the perimeter of said head portion, thedistance between all opposed portions of the walls defining said slitsbeing greater than the transverse dimension of said shank at the portionof said shank immediately below said head, said welding pins beingstacked with the under surface of the head portion of each pin disposedparallel to and adjacent the upper surface of the head portion of thenext lower pin and the shank portion of each upper pin extendingdownwardly through the space defined between the slits of the next lowerpin and lying in parallel adjacent relation to the shank of said lowerpin, whereby each pin may be moved laterally relative to the nextadjacent pin in a separating direction of said shanks withoutinterference between said pins, the longitudinal axis of the shank ofany pin in said stack being angularly related to a line extendingthrough the tips of said stacked pins.